Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$93.77	12.685%	$105.6647	$105.66	$105.65	$105.70
Purchase #2	$234.48	3.827%	$243.4535	$243.45	$243.45	$243.50
Purchase #3	$11.66	9.526%	$12.7707	$12.77	$12.75	$12.80
Purchase #4	$213.38	7.539%	$229.4667	$229.47	$229.45	$229.50
Purchase #5	$214.66	8.646%	$233.2195	$233.22	$233.20	$233.20
Purchase #6	$17.32	9.322%	$18.9346	$18.93	$18.95	$18.90
Purchase #7	$162.33	4.452%	$169.5569	$169.56	$169.55	$169.60
7 purchase totals =	$947.60		$1,013.0666	$1,013.06	$1,013.00	$1,013.20